1. Field
The present disclosure relates generally to communication, and more specifically to controlling transmit power in a wireless communication system.
2. Background
The 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) represents a major advance in cellular technology and is the next step forward in cellular 3G services as a natural evolution of a Global system for mobile communications (GSM) and a Universal Mobile Telecommunications System (UMTS). LTE provides for an uplink speed of up to 50 megabits per second (Mbps) and a downlink speed of up to 100 Mbps and brings many technical benefits to cellular networks. LTE is designed to meet carrier needs for high-speed data and media transport as well as high-capacity voice support well into the next decade. Bandwidth is scalable from 1.25 MHz to 20 MHz. This suits the needs of different network operators that have different bandwidth allocations, and also allows operators to provide different services based on the spectrum. LTE is also expected to improve spectral efficiency in 3G networks, allowing carriers to provide more data and voice services over a given bandwidth. LTE encompasses high-speed data, multimedia unicast and multimedia broadcast services.
The LTE physical layer (PHY) is a highly efficient means of conveying both data and control information between an enhanced base station (eNodeB) and mobile user equipment (UE). The LTE PHY employs some advanced technologies that are new to cellular applications. These include Orthogonal Frequency Division Multiplexing (OFDM) and Multiple Input Multiple Output (MIMO) data transmission. In addition, the LTE PHY uses Orthogonal Frequency Division Multiple Access (OFDMA) on the downlink (DL) and Single Carrier-Frequency Division Multiple Access (SC-FDMA) on the uplink (UL). OFDMA allows data to be directed to or from multiple users on a subcarrier-by-subcarrier basis for a specified number of symbol periods.
Given increasing deployments of heterogeneous networks, transmit power control is becoming a greater challenge, successfully being received by an intended recipient without causing undue interference to others. In advanced communication protocols such as LTE, setting an appropriate transmit power creates challenges due to the number of control and data channels that are transmitted. In particular, it is desirable to minimize user equipment (UE) transmit power while achieving desired traffic and overhead performance on an uplink (UL) channel.